Selenocystine induces oxidative-mediated DNA damage via impairing homologous recombination repair of DNA double-strand breaks in human hepatoma cells

Paeonol enhances a recombinant EGFR-targeted fusion protein-drug conjugate induced antitumor efficacy in esophageal cancer

Esophageal cancer (EC) is a gastrointestinal cancer with high morbidity and mortality, along with a low 5-year survival rate, which urgently requires the discovery of new drugs for prevention and treatment. Our previous studies have found a novel EGFR-targeted fusion protein-drug conjugate, Fv-LDP-D3-AE, which exhibits significant inhibitory activity against esophageal cancer. However, the effectiveness of monotherapy still faces major challenges in clinical translation for esophageal cancer treatment. Therefore, there is an urgent need to identify a candidate anti-tumor drug that can be combined with Fv-LDP-D3-AE to enhance therapeutic efficacy. In this study, we report a novel combination treatment regimen of paeonol with Fv-LDP-D3-AE, using human esophageal cancer cells KYSE70 and EC109 for in vitro studies and establishing a BALB/c nude mouse xenograft model for in vivo experiments to investigate the anti-tumor efficacy and potential mechanisms of the combination therapy in esophageal cancer. The results indicated that the combined treatment emerged a synergistic effect, which could effectively inhibit the proliferation, migration, and invasion of esophageal cancer cells, induce more obvious cell apoptosis and DNA damage, and suppress tumor growth in the xenograft mouse model with a tumor inhibition rate of 76%. This may be attributed to the combination therapy simultaneously inhibiting the EGFR/AKT/mTOR signaling pathway and downregulating the expression of nucleolin. Overall, these findings suggest that paeonol could synergize with Fv-LDP-D3-AE to enhance anti-esophageal cancer efficacy, which may be a promising therapeutic strategy for esophageal cancer.

Exposure to Selenomethionine and Selenocystine Induces Redox-Mediated ER Stress in Normal Breast Epithelial MCF-10A Cells

Selenium is an essential trace element co-translationally incorporated into selenoproteins with important biological functions. Health benefits have long been associated with selenium supplementation. However, cytotoxicity is observed upon excessive selenium intake. The aim of this study is to investigate the metabolic pathways underlying the response to the selenium-containing amino acids selenomethionine and selenocysteine in a normal human breast epithelial cell model. We show that both selenomethionine and selenocystine inhibit the proliferation of non-cancerous MCF-10A cells in the same concentration range as cancerous MCF-7 and Hela cells, which results in apoptotic cell death. Selenocystine exposure in MCF-10A cells caused a severe depletion of free low molecular weight thiols, which might explain the observed upregulation of the expression of the oxidative stress pathway transcription factor NRF2. Both selenomethionine and selenocystine induced the expression of target genes of the unfolded protein response (GRP78, ATF4, CHOP). Using a redox-sensitive fluorescent probe targeted to the endoplasmic reticulum (ER), we show that both selenoamino acids shifted the ER redox balance towards an even more oxidizing environment. These results suggest that alteration of the redox state of the ER may disrupt protein folding and cause ER stress-induced apoptosis in MCF-10A cells exposed to selenoamino acids.

Unveiling the Role of Selenium in Child Development: Impacts on Growth, Neurodevelopment and Immunity

Selenium (Se) is a vital trace element for children, playing a crucial role in numerous physiological processes, including antioxidant defense, immune regulation, thyroid function, and bone metabolism. Emerging evidence highlights its potential impact on child development and growth while also underscoring the complexity of its mechanisms and the global variations in Se intake. The aim of this review is to comprehensively elucidate the significance of Se in various biological processes within the human body, with a focus on its role in child development and growth; its biochemical effects on the nervous system, thyroid function, immune system, and bone tissue; and the implications of Se deficiency and toxicity. This review integrates findings from experimental models, epidemiological studies, and clinical trials to explore Se's role in neurodevelopment, growth regulation, and immune competence in children. Selenoproteins, which regulate oxidative stress and thyroid hormone and bone metabolism, are essential for normal growth and cognitive development in children. Se deficiency and toxicity has been linked to impaired immune function, growth retardation, and decreased immune function. The findings underscore Se's influence on various biological pathways that are critical for healthy child development and its broader importance for child health. Public health strategies aimed at optimizing selenium intake may play a pivotal role in improving pediatric health outcomes worldwide.

Se-methylselenocysteine inhibits inflammatory response in an LPS-stimulated chicken HD11 macrophage-like cell model through the NFKB2 pathway

Among the various sources of selenium supplementations, the Se-methylselenocysteine (SeMC) is a natural organic selenium compound that has been demonstrated to have multiple advantages in terms of metabolism efficiency and biosafety in animals. Nevertheless, the genome-wide impact of SeMC on gene transcription remains to be elucidated. In this study, we employed an LPS-stimulated chicken HD11 macrophage-like cell model to identify the principal transcription factors involved in transcriptome regulation responsible for SeMC treatment. RNA-seq identified 3,263 transcripts that exhibited a statistically significant differential expression between the SeMC-treated group and the control group and 1,344 transcripts that exhibited a statistically significant differential expression between the LPS + SeMC- and LPS-treated groups (FDR < 0.05, FDR > 1.5). The bioinformatic analysis identified six transcription factors (NFKB2, RFX2, E2F5, ETV5, BACH1, and E2F7) as potential candidate genes for transcriptome regulation in SeMC-treated HD11 cells. Subsequent experimental verification demonstrated that SeMC suppressed the inflammatory response in an LPS-stimulated chicken HD11 cell model via the TXN2-NF-κB pathway. The administration SeMC was observed to reduce the production of ROS as well as the transcription and translation of inflammatory cytokines in both cell culture and in vivo animal studies. One candidate pathway by which SeMC exerts its effects is through the targeting of the transcription factor, NFKB2, by selenoprotein TXN2. This study identified key transcription factors and revealed one of the potential mechanisms through which SeMC exerts its anti-inflammatory effects from the perspective of transcriptional regulation.

Enhancing cisplatin efficacy in hepatocellular carcinoma with selenocystine: The suppression of DNA repair and inhibition of proliferation in hepatoma cells

Cisplatin (cDDP) is a crucial chemotherapy drug for treating various cancers, including hepatocellular carcinoma (HCC). However, its effectiveness is often hindered by side effects and drug resistance. Selenocystine (SeC) demonstrates potential as an anticancer agent, particularly by inhibiting DNA repair mechanisms. This study explored the synergistic potential of SeC combined with cDDP for treating HCC. Our results show that SeC pretreatment followed by cDDP significantly suppresses HCC cell proliferation more effectively than either treatment alone, with minimal toxicity to normal liver cells. The combination induces significant DNA damage by inhibiting homologous recombination (HR) and non-homologous end joining (NHEJ) pathways. Xenograft experiments confirmed that the combined therapy strongly inhibits tumor growth. SeC boost the effectiveness of cDDP by amplifying DNA damage and inhibiting DNA repair, presenting a promising approach to enhancing liver cancer treatment.

Combined in vitro and in silico mechanistic approach to explore the potential of Alternaria mycotoxins alternariol and altertoxin II to hamper γH2AX formation in DNA damage signaling pathways

Risk assessment of food and environmental contaminants is faced by substantial data gaps and novel strategies are needed to support science-based regulatory actions. The Alternaria mycotoxins alternariol (AOH) and altertoxin II (ATXII) have garnered attention for their possible genotoxic effects. Nevertheless, data currently available are rather scattered, hindering a comprehensive hazard characterization. This study combined in vitro/in silico approaches to elucidate the potential of AOH and ATXII to induce double-strand breaks (DSBs) in HepG2 cells. Furthermore, it examines the impact of co-exposure to AOH and the DSB-inducing drug doxorubicin (Doxo) on γH2AX expression. AOH slightly increased γH2AX expression, whereas ATXII did not elicit this response. Interestingly, AOH suppressed Doxo-induced γH2AX expression, despite evidence of increased DNA damage in the comet assay. Building on these observations, AOH was postulated to inhibit γH2AX-forming kinases. Along this line, in silico analysis supported AOH potential interaction with the ATP-binding sites of these kinases and immunofluorescence experiments showed decreased intracellular phosphorylation events. Similarly, in silico results suggested that ATXII might also interact with these kinases. This study emphasizes the importance of understanding the implications of AOH-induced γH2AX expression inhibition on DNA repair processes and underscores the need for caution when interpreting γH2AX assay results.

Gss deficiency causes age-related fertility impairment via ROS-triggered ferroptosis in the testes of mice

Glutathione synthetase (GSS) catalyzes the final step in the synthesis of glutathione (GSH), a well-established antioxidant. Research on the specific roles of the Gss gene during spermatogenesis remains limited due to the intricate structure of testis. In this study, we identified pachytene spermatocytes as the primary site of GSS expression and generated a mouse model with postnatal deletion of Gss using Stra8-Cre (S8) to investigate the role of GSS in germ cells. The impact of Gss knockout on reducing male fertility is age-dependent and caused by ferroptosis in the testis. The 2-month-old S8/Gss-/- male mice exhibited normal fertility, due to a compensatory increase in GPX4, which prevented the accumulation of ROS. With aging, there was a decline in GPX4 and an increase in ALOX15 levels observed in 8-month-old S8/Gss-/- mice, resulting in the accumulation of ROS, lipid peroxidation, and ultimately testicular ferroptosis. We found that testicular ferroptosis did not affect spermatogonia, but caused meiosis disruption and acrosome heterotopia. Then the resulting aberrant sperm showed lower concentration and abnormal morphology, leading to reduced fertility. Furthermore, these injuries could be functionally rescued by inhibiting ferroptosis through intraperitoneal injection of GSH or Fer-1. In summary, Gss in germ cells play a crucial role in the resistance to oxidative stress injury in aged mice. Our findings deepen the understanding of ferroptosis during spermatogenesis and suggest that inhibiting ferroptosis may be a potential strategy for the treatment of male infertility.

Selenium-Containing Agents Acting on Cancer-A New Hope?

Selenium-containing agents are more and more considered as an innovative potential treatment option for cancer. Light is shed not only on the considerable advancements made in understanding the complex biology and chemistry related to selenium-containing small molecules but also on Se-nanoparticles. Numerous Se-containing agents have been widely investigated in recent years in cancer therapy in relation to tumour development and dissemination, drug delivery, multidrug resistance (MDR) and immune system-related (anti)cancer effects. Despite numerous efforts, Se-agents apart from selenocysteine and selenomethionine have not yet reached clinical trials for cancer therapy. The purpose of this review is to provide a concise critical overview of the current state of the art in the development of highly potent target-specific Se-containing agents.

Blockage of Nrf2 and autophagy by L-selenocystine induces selective death in Nrf2-addicted colorectal cancer cells through p62-Keap-1-Nrf2 axis

Persistent Nrf2 activation is typically noted in many cancers, including colorectal cancer (CRC), aiding cancer cells in overcoming growth stress and promoting cancer progression. Sustained Nrf2 activation, which is beneficial for cancer cells, is called "Nrf2 addiction"; it is closely associated with malignancy and poor prognosis in patients with cancer. However, Nrf2 inhibitors may have adverse effects on normal cells. Here, we found that the selenocompound L-selenocystine (SeC) is selectively cytotoxic in the Nrf2-addicted CRC cell line WiDr cells, but not in non-Nrf2-addicted mesenchymal stem cells (MSCs) and normal human colon cells. Another CRC cell line, C₂BBe₁, which harbored lower levels of Nrf2 and its downstream proteins were less sensitive to SeC, compared with the WiDr cells. We further demonstrated that SeC inhibited Nrf2 and autophagy activation in the CRC cells. Antioxidant GSH pretreatment partially rescued the CRC cells from SeC-induced cytotoxicity and Nrf2 and autophagy pathway inhibition. By contrast, SeC activated Nrf2 and autophagy pathway in non-Nrf2-addicted MSCs. Transfecting WiDr cells with Nrf2-targeting siRNA decreased persistent Nrf2 activation and alleviated SeC cytotoxicity. In KEAP1-knockdown C₂BBe₁ cells, Nrf2 pathway activation increased SeC sensitivity and cytotoxicity. In conclusion, SeC selectively attacks cancer cells with constitutively activated Nrf2 by reducing Nrf2 and autophagy pathway protein expression through the P62-Nrf2-antioxidant response element axis and eventually trigger cell death.